Spinal

1. Formation and general organization of the spinal nerves 2. Dorsal roots and ventral roots 3. Spinal ganglia 4. Zonal and segmental innervation 5. Plexuses and peripheral distributions Spinal nerves General organization  31 pairs of segmentally arranged nerves:  8 cervical – C1-C8  12 thoracic –Th1-Th12  5 lumbar –L1-L5  5 sacral –S1-S5  1 coccygeal –Co1  corresponds to a pair of embryonic somites  emerges through the intervertebral foramen  mixed (common nerve trunk)

 topographic relationships between spinal nerves, segments and vertebrae Prof. Dr. Nikolai Lazarov 2 Spinal nerves Spinal nerve formation

 ventral (motor) root:  axons of neurons in anterior and lateral grey columns  motor and autonomic (sympathetic and parasympathetic)  dorsal (sensory) root:  central processes of the dorsal ganglion cells  convey somatic and visceral sensory information

Prof. Dr. Nikolai Lazarov 3 Spinal nerves Spinal ganglion

 spindle-shaped aggregations on the dorsal roots – dorsal root ganglion  (pseudo)unipolar neurons – ovoid or spherical (primary afferent neurons)  satellite cells (capsular cells, amphicytes)  Schwann cells and blood vessels  embryonic origin – neural crest cells  location – in intervertebral foramina  axons (afferents) – proximal and distal processes  functional modalities:  mechanoreception  nociception  proprioception

Prof. Dr. Nikolai Lazarov 4 Spinal nerves Formation of a dermatome

 Dermatome – a localized area of skin supplied by a single nerve from a single nerve root of the spinal cord  herringbone pattern – the width of the cutaneous field of innervation  thorax&abdomen – like a stack of discs  arms&legs – longitudinally along the limbs  Peripheral nerve field – a territory supplied by a peripheral nerve from more than one somite

Prof. Dr. Nikolai Lazarov 5 Spinal nerves Dermatome vs. skin innervation

Prof. Dr. Nikolai Lazarov 6 Spinal nerves Zonal innervation

 Sensory nerve innervation regions:  autonomic  anesthesia  mixed  hypoesthesia  maximal  no loss in sensibility

Prof. Dr. Nikolai Lazarov 7 Spinal nerves Segmental innervation

 Segmental innervation:  organs or muscles innervated by one spinal segment  corresponds to the general metamerism of the body  Embryonic somites (metamere):  myotome  muscle  sclerotome  skeleton  dermatome  skin  Neuromere  somite

Prof. Dr. Nikolai Lazarov 8 Spinal nerves Spinal nerve trunks  Spinal nerve functional components:  somatic components – efferent and afferent fibers  visceral components – sympathetic or parasympathetic  Spinal nerve branches:  meningeal branch – at all vertebral levels (recurrent meningeal nerve)  white ramus communicans – myelinated preganglionic fibers  all thoracic and L1-L2 to corresponding sympathetic ganglion  S2-S4 nerves to the parasympathetic pelvic plexus  grey ramus communicans – unmyelinated postganglionic fibers  from paravertebral sympathetic ganglia  ventral (anterior) ramus – thicker  ventrolateral muscles  skin of the trunk and extremities  dorsal (posterior) ramus – thinner  intrinsic dorsal muscles of the back and neck  overlying skin from vertex to coccyx

Prof. Dr. Nikolai Lazarov 9 Spinal nerves Dorsal rami of the spinal nerves

 divide into medial and lateral branches (exception C1)  have a typical segmental distribution  cervical dorsal rami:  (C1) – purely motor  (C2) – mixed  C3 medial cutaneous branch,  thoracic dorsal rami:  Th1-Th6 – medial (mixed) and lateral (motor) branch  Th7-Th12 – medial (motor) and lateral (mixed)  lumbar dorsal rami:  L1-L3 lateral cutaneous branches – superior clunial nerves  sacral dorsal rami:  S1-S3 lateral cutaneous branches – medial clunial nerves

Prof. Dr. Nikolai Lazarov 10 Spinal nerves Ventral rami of the spinal nerves

 Thoracic ventral rami – 12 pairs:  segmental distribution –  Th12 – subcostal nerve  anterior cutaneous branches  lateral cutaneous branches

Prof. Dr. Nikolai Lazarov 11 , plexus cervicalis  Formation and segmental origin:  ventral rami of C1-C4 nerves  Branches:  superficial (sensory) branches :  lesser occipital nerve, n. occipitalis minor  great auricular nerve, n. auricularis magnus  transverse colli nerve, n. transversus colli  supraclavicular nerves, nn. supraclaviculares  deep (motor) branches:  muscular branches, rr. musculares  inferior root of the ansa cervicalis, radix inferior ansae cervicalis  trapezius root, ramus trapezius  sternocleidomastoid root, r. sternocleidomastoideus  phrenic nerve, n. phrenicus

Prof. Dr. Nikolai Lazarov 12 , plexus brachialis

 Formation and segmental origin:  ventral rami of C5-C8, Th1 nerves  Three primary trunks:  superior (upper) trunk – C5-C6  middle trunk – C7  inferior (lower) trunk – C8-Th1  Divisions:  posterior division  posterior cord  anterior  lateral cord  medial cord

Prof. Dr. Nikolai Lazarov 13 Brachial plexus, plexus brachialis  Main branches:  supraclavicular part:  dorsal scapular nerve, n. dorsalis scapulae  long thoracic nerve, n. thoracicus longus  nerve to the subclavius, n. subclavius  suprascapular nerve, n. suprascapularis  infraclavicular part:  lateral cord, fasciculus lateralis: • musculocutaneous nerve, n. musculocutaneus • lateral root of median, radix lateralis n. mediani  medial cord, fasciculus medialis: • medial root of median, radix medialis n. mediani • ulnar nerve, n. ulnaris • medial cutaneous of arm, n. cutaneus brachii medialis • medial cutaneous of forearm, n. cutaneus antebrachii medialis  posterior cord, fasciculus posterior: • axillary nerve, n. axillaris • radial nerve , n. radialis

Prof. Dr. Nikolai Lazarov 14 Brachial plexus, plexus brachialis

 Brachial distribution of:  musculocutaneous nerve  median nerve  ulnar nerve  radial nerve  Forearm innervation:  median nerve  ulnar nerve  radial nerve  Hand innervation:  median nerve  ulnar nerve

Prof. Dr. Nikolai Lazarov 15 Muscle innervation of the upper limb

 Muscular branches of:  median nerve  ulnar nerve  radial nerve

Prof. Dr. Nikolai Lazarov 16 Cutaneous innervation of the upper limb

Prof. Dr. Nikolai Lazarov 17 Peripheral neuropathies

 Radial nerve palsy, wrist drop (Saturday night palsy)  Ulnar nerve palsy, ‘claw hand’ handlebar palsy – cyclist’s hands

 Median nerve palsy,‘accoucheur's hand’ median neuropathy (Carpal tunnel syndrome) –

Prof. Dr. Nikolai Lazarov 18 Lumbosacral plexus, plexus lumbosacralis  , plexus lumbalis:  formation and segmental origin: ventral rami of Th12, L1-L4 nerves

 , plexus sacralis:  formation and segmental origin:  Coccygeal plexus, plexus coccygeus: ventral rami of L5, S1-S5, Co1 nerves  ventral rami of S5,Co1 Prof. Dr. Nikolai Lazarov 19 Lumbar plexus, plexus lumbalis

 Branches:  muscular branches, rr. musculares  purely sensory branch:  lateral femoral cutaneous nerve, n. cutaneus femoris lateralis  sensorimotor branches:  , n. iliohypogastricus  , n. ilioinguinalis  genitofemoral nerve, n. genitofemoralis  obturator nerve, n. obturatorius  femoral nerve, n. femoralis

Prof. Dr. Nikolai Lazarov 20 Obturator nerve, n. obturatorius

 passes through obturator canal  branches – L2-L4:  anterior division  posterior division  motor branches:  adductor muscles  gracilis muscle  sensory branches:  inner surface of the thigh  accessory obturator nerve, n. obturatorius accessorius

Prof. Dr. Nikolai Lazarov 21 Obturator nerve, n. obturatorius

 passes through obturator canal  branches – L2-L4:  anterior division  posterior division  motor branches:  adductor muscles  gracilis muscle  sensory branches:  inner surface of the thigh  accessory obturator nerve, n. obturatorius accessorius

Prof. Dr. Nikolai Lazarov 22 Femoral nerve, n. femoralis  passes through lacuna musculorum  branches – L2-L4:  muscular branches, rr. musculares:  iliopsoas  pectineus  sartorius  extensor muscles of the knee – quadriceps femoris  sensory branches:  anterior femoral cutaneous nerve  saphenous nerve

Prof. Dr. Nikolai Lazarov 23 Sacral plexus, plexus sacralis  Branches:  motor branches:  muscular branches, rr. musculares  superior gluteal nerve, n. gluteus superior  inferior gluteal nerve, n. gluteus inferior  purely sensory branch:  posterior femoral cutaneous nerve n. cutaneus femoris posterior  sensorimotor branches:  pudendal nerve , n. pudendus  coccygeal nerve, n. coccygeus  sciatic nerve, n. ischiadicus  visceral branch:  pelvic splanchnic nerve, nervus erigens Prof. Dr. Nikolai Lazarov 24 Sciatic nerve, n. ischiadicus  passes through foramen infrapiriforme  Main branches:  tibial nerve, n. tibialis:  articular branches  muscular branches  sural nerve  medial and lateral calcaneal  medial and lateral plantar nerves  common peroneal nerve, n. peroneus communis:  superficial peroneal nerve (musculocutaneous)  deep peroneal nerve (anterior tibial nerve)

Prof. Dr. Nikolai Lazarov 25 Spinal nerves Saturday night palsy

Thank you…

Prof. Dr. Nikolai Lazarov 26